Dental setup



July 7, 1959 J. D. SCHWARTZ DENTAL SETUP Filed Feb. 11, 1957 W aw? B 2,893,054 DENTAL SETUP Jacob Daniel Schwartz, Pittsburgh, Pa.

Application February 11, 1957, Serial No. 639,407

4 Claims. (Cl- IS-5.7)

This invention relates in general to forming a plaster of Paris mold for producing an artificial denture and more particularly to plastic pins for use in anchoring the artificial teeth of the denture to the plaster of Paris in the mold. 1 r

The crowns of artificial teeth are free of under cuts. This is necessarily so because artificial teeth are molded in metal molds and the teeth must be free of undercuts to permit their withdrawal from the metal molds.

Consequently, as a result of being free of undercuts they are readily freed and displaced from their'invested position in a plaster of Paris mold during the process of producing an artificial denture. Then'when the denture is finishedthe displaced teeth will be found to be malposed in the denture and elaborate steps must be taken to reset them in proper position.

Displacement of a tooth in partial denture molds is particularly disastrous because in those molds the teeth are usually banked, that is the teeth are almost completely covered with plaster of Paris and being out of sight it cannot readily be determined if any teeth have been displaced. And being out of reach it is most difficult if not impossible to reseat the teeth.

To overcome this disadvantage, by providing means for preventing artificial teeth from becoming displaced from their seats in a plaster of Paris denture mold, I invented and patented Patent No. 2,585,857, an artificial tooth with a small opening or slot in the neck of the tooth for receiving one end of a small round, elongated plastic pin. The plastic pin being relatively long and extending outwardly beyond the denture, its other end was enveloped and held by the plaster of Paris of the mold. Thus with one end of the pin nested in the tooth and the other end in plaster of Paris, the tooth wassecurely anchored to its seat in the plaster of Paris denture mold. The pin, of course, was applied to the tooth while it was positioned in the denture when the denture was in wax form, prior to investment thereof in a denture flask.

But since the small opening or slot in the neck of the tooth is normally covered with wax, in a waxed-up denture, I found that when I inserted the end of the pin into the softened wax surrounding the neck of the tooth, I could not always makeactual contact of the pin with the tooth. Although the gap between the neck of the tooth and the body of the round plastic pin was slight, it was oft times sufiicient to allow the tooth to roll out laterally from its invested seat inthe plaster of Paris denture mold.

Therefore, the principal object of this invention'is 'to provide a plastic pin, foranchoring an artificial tooth to its plaster of Paris seat in a denture mold, said pin having a special form, whereby to easily maneuver one end of the pin into actual contact with the periphery of the neck of an artificial tooth, when the tooth is positioned in a denture in wax form.

Another object is to provide a plastic anchoring pin,

as described in the principal object, which is composed td States. Patent of material identical with the plastic material forming the body of a denture, whereby the pin will be indistinguishable on the surface of the finished denture.

Another object is to provide a plastic anchoring pin having at least two different thicknesses in its cross-sectional outline and a method for bringing said pin into actual contact with the periphery of the neck of a tooth, when said tooth is positioned in a denture in wax form.

These and other objects will become apparent in the following description and the drawing, in which:

Figure 1 is a perspective view of a plastic pin as provided in the present invention,

Figure 2 shows the buccal surface of a posterior tooth and also shows two positions of the end view of the plastic pin in relation to the periphery of the neck of the tooth,

Figure 3 shows a cross-sectional view of a portion of a waxed-up denture on a gypsum product cast that is, a cast formed of hard plaster of Paris, known in the dental art as artificial stone; it is a product formed from gypsum, its composition is identical with common plaster of Paris, but it is much harder, due to the method of manufacturing it. At this stage in the process of producing a finished artificial plastic denture, this assembly is commonly called the set-up or the wax set up, and as shown in the draw ing, comprises a cast of a jaw, formed of artificial stone, having a coating or layer of wax on its surface, that is, the surface of the cast corresponding or simulating the tissue surface of the jaw, which is shaped to form the pattern of the base for the finished denture, and an artificial tooth set in this wax, in desired position, also, showing the plastic pin, in a perspective view, held by the hardened wax in proper contact with the periphery of the neck of the tooth, prior to investment in a denture flask,

Figure 4 showsa cross-sectional view of a section of a denture flask, showing two posterior teeth invested therein in plaster of Paris, and also shows the plastic pins held by the plaster of Paris investment in proper contact position with the periphery of the neck of the teeth.

Generally speaking, the present invention overcomes the difficulties encountered in the use of plastic anchoring pins as provided heretofore, by providing an elongated plastic pin having a cross-sectional outline which is other than circular. That is, when the cross-section is substantially at a right angle to the length or axis of the pin. For example, semi-circular, square, triangular, elliptical, etc. These various cross-sectional outlines have at least two different thicknesses. Specifically, for example, a semi-circular cross-sectional outline, the width of one thickness being the diameter thereof and the other width, the radius thereof. Thus, if one end of this novel pin is inserted into the pre-softened gingival wax of a waxed-up denture and brought close to the periphery of the neck of a tooth therein, in a manner whereby the short width, to wit, the radius, of the pins thicknesses lies axially of the tooth, and the pin is then rotated axially until its long width, to wit, the diameter, lies axially of the tooth, the increase in the Width of the pin, running axially of the tooth, will cause the pin to Wedge between the rapidly hardening wax and the periphery of the neck of the tooth, thereby efiecting a positivecontact of the pin with the tooth.

Considering now the drawing to obtain a clearer understanding and appreciation of this invention, the plastic pin 5 is shown here with a preferred embodiment thereof, to wit, an elongated pin having a cross-sectional outline of a segment of a circle. The width of the'straight edge 6 being its greatest thickness and the distance between this line and the top of the are 7 being its smallest thickness. It may have any cross-sectional outline other than circular. The length 8 of the pin 5 is not critical, It must however be of sufiicient length to extend outwardly from the periphery 9 of the neck 10 of the tooth 11 beyond the wax flange 12. of the waxed-up denture, 'where it can be enveloped by the soft plaster of Paris during the investment of the waxed-up denture in the denture flask section 15.

In actual practice, after the denture is waxed-up on a gypsum cast 18, with all teeth in proper position therein, a pointed metal instrument is heated and pierced into the wax 12. surrounding and adjacent to the top of the periphery 9 of the tooth 11. This action is taken to soften a localized portion of the wax 12 to permit entry therein of an end portion 16 of the plastic pin 5. One end 16 of the pin is then inserted into the localized softened wax, with its smallest width thickness running axially, of the tooth 11, as shown by the dotted line crosssectional outline of the pin 5 in Figure 2. An effort being made at the same time to bring the pin 5 as close to the periphery 9 of the tooth it as possible. The pin 5 is then grasped at its free end 19 with the fingers and rotated axially until its greatest width thickness 6 is running axially of the tooth 11. This: will cause the pin 5 to wedge between the rapidly hardening wax 12 and the periphery 9 of the neck of the tooth ill. All of which is shown in Figure 2. The dotted outline of the pin 5 shows it as originally inserted close to the top 9 of the tooth 11. The solid outline shows the pin 5 rotated axially, its greatest thickness 6 running axially of the tooth 11 and making contact with the top of the tooth 11. The case is now invested with plaster of Paris 14 in a denture flask 15.

Since the pin 5 is of suificient length to extend from the above described contact point outwardly beyond the surface of the wax 12, it will be surrounded by the soft investment plaster 14 contained in the metal flask section 15, and maintained in this position when the investment plaster 14 becomes hard.

Thus when the wax 12 which holds the pin 5 against the tooth 11, is melted and flushed out of the flask section 15, the pin 5 will still bear against the periphery 9 of the neck of the tooth 11 and anchor it to its seat 17 in the investment material 14. Also in the subsequent steps of filling the mold with soft plastic material and processing the same, the tooth 11 will not 'be displaced from its seat 17 in the plaster of Paris investment 14.

The pin 5 is composed of the identical plastic material which forms the base of the finished denture (not shown). The pin 5, however being in a polymerized or hardened state when originally used in the waxed-up denture. When the denture is processed the plastic material of the denture base will unite with the plastic pin 5, and since its color is identical with the plastic base of the finished denture, its identity will be lost and it will be indistinguishable on the labiobuccal surface of the denture.

Having described the invention in one of its preferred embodiments, it being clearly understood that other forms and constructions may be made without departing from the spirit of the invention, I claim:

1 The method of anchoring an artificial tooth to a plaster of Paris mold, said mold formed by investing an artificial denture having a wax base and containing said tooth therein with plaster of Paris in a denture flask, comprising softening a portion of the flange of said wax base apically to and closely adjacent the periphery of the neck of said toot'rrwith a suitable, heated instrument, such as a pointed metal instrument, inserting into said heat softened portion an end of a rigid, elongated pin, composed of polymerized plastic and having at least two different thicknesses in its cross-sectional aspect, in a manner having the long axis of said pin lying transversely to the long axis of said tooth and having said inserted end lying lingually beyond and closely adjacent said periphery and having the other end of said pinextending outwardly beyond said flange, to enable the pin to be graspedwith fingers to rotate it axially, and having a short thickness of said pin extending substantially in the direction of the long axis of said tooth, rotating said pin axially, while said heat softened portion of said wax flange is still soft, to extend the pins long thickness in the direction of the long axis of said tooth until the axial surface of said pin is brought into contact with the periphery of the neck of said tooth, allowing said softened wax to cool and harden, then investing said denture, with said pin attached, with plaster of Paris, in a denture flask.

2. In the method of anchoring an artificial tooth to a plaster of Paris mold formed by investing an artificial denture having a wax base and containing said tooth therein, with plaster of Paris, in a denture flask, the steps comprising softening a portion of the flange of said wax base apically to and closely adjacent the periphery of the neck of said tooth with a suitable, heated instrument, such as a pointed metal instrument, inserting into said heat softened portion an end of a rigid, elongated pin, composed of polymerized plastic and having at least two different thicknesses in its cross-sectional aspect, in a manner having the long axis of said pin lying transversely to the long axis of said tooth and having said inserted end lying lingually beyond and closely adjacent said periphery and having the other end of said pin extending outwardly beyond said flange, to enable the pin to be grasped with fingers to rotate it axially, and having a short thickness of said pin extending substantially in the direction of the long axis of said tooth, rotating said pin axially, while said heat softened portion of said wax flange is still soft, to extend the pins long thickness in the direction of the long axis of said tooth until the axial surface of said pin is brought into contact with the periphery of the neck of said tooth allowing said softened wax to cool and harden.

3. The method of anchoring an artificial tooth to a mold formed of plaster of Paris for producing therein a finished denture having a polymerized plastic base, suitable for dentures, said mold formed by investing an artificial denture having a wax base and containing said tooth therein,'with plaster of Paris in a denture flask, comprising softening a portion of the flange of said wax base apically to and closely adjacent the periphery of the neck of said tooth with a suitable, heated instrument, such as a pointed metal instrument, inserting into said L heat softened portion an end of a rigid, elongated pin,

composed of polymerized plastic identical with that forming the base of said finished denture and having at least two different thicknesses in its cross-sectional aspect, in a manner having the long axis of said pin lying trans- Y versely to the long axis of said tooth and having said inserted end lying slightly, lingually beyond and closely adjacent said periphery and having the other end of said pin extending outwardly beyond said flange, to enable the pin to be grasped with fingers to rotate it axially, and having a short thickness of said pin extending substantially in the direction of the long axis of said tooth, rotating said pin axially, while said heat softened portion of said wax flange is still soft, to extend the pins long thickness in the direction of the long axis of said tooth until the axial surface of said pin is brought into contact with the periphery of the neck of said tooth, allowing said softened wax to cool and harden, then investing said denture, with said pin attached, with plaster of Paris, in a denture flask.

4. In an artificial denture set-up, comprising a cast of a jaw, formed of artificial stone, a coating of wax on the tissue surface of said cast, shaped to form the pattern of the base of the finished denture, and at least one artificial tooth, set in said wax coating in desired position, a plastic positioning pin, said pin comprising a rigid, elongated body of polymerized plastic, having a flesh color, said pin having at least two different thicknesses in its cross-sectional aspect, said pin being positioned in said set-up in a manner having its long axis lying transversely to the long axis of said tooth, one end of said pin being embedded in the flange portion of said wax coating, the axial surface of said pin being in contact with the periphery of the neck of said tooth, the long thickness of said pin extending substantially in the direction of the long axis of said tooth, the embedded end of said pin extending lingually beyond the periphery of the neck of said tooth and the other end of said pin lying outwardly beyond said flange portion of said wax coating, where it can be enveloped and held by plaster of Paris when said set-up containing said pin is invested with plaster of Paris in a denture flask.

References Cited in the file of this patent UNITED STATES PATENTS 

